Proximal Growth of the Column in Bathycrinid Crinoids (Echinodermata) Following Decapitation
Abstract:Individuals of the bathycrinid crinoids Democrinus chuni (Döderlein) and Democrinus brevis (A. H. Clark) remain upright following loss of the crown and proximal column. The axial canal is sealed in the apical part of the column by stereomic calcite overgrowth, and radice-like extensions are generated; one specimen has a more globular, gall-like growth, suggesting parasitic infestation. Oxygen and nutrients were presumably absorbed through the ectoderm in these “headless” crinoids. Evidence of breakage and the absence of autotomy planes in the mesistele of Democrinus imply that crown loss was probably due to predation. These specimens represent about 1.6% of the examined sample. The life expectancy of mutilated specimens was presumably short. Analogous patterns of regeneration are known from as far back as the Ordovician.
Document Type: Research Article
Publication date: November 1, 1997
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